Grigor Dimitrov is not the player I would have pegged as a threat to Rafael Nadal’s eight-year winning streak in Monte Carlo. It’s true, the last time they played, in Rotterdam in 2009, the then-teenage Bulgarian had taken a set. But that was an indoor hard court, and this was outdoor clay—and not just any outdoor clay, but Nadal’s favorite outdoor clay. More important, for all of his florid skill, Dimitrov’s weakness is simple and straightforward: the high one-handed backhand. They don’t call him Baby Federer for nothing.

I thought Nadal would be able to exploit that backhand the same way he has always exploited Federer’s, and for a set he did. Nadal did more than that, in fact, moving forward quickly, roping his forehand down the line, making virtually all of his first serves, and watching as Dimitrov, who started well, began to overhit. Rafa won a routine first set, 6-2, in 31 minutes.

In the second, though, Dimitrov changed the rhythm and the momentum of the match with a play that has also worked for Federer against Nadal at times: the drop shot. Half a dozen times Dimitrov, who has terrific feel with all of his shots, pulled Rafa forward and won the cat-and-mouse scramble that ensued. Nadal, thrown off, began to struggle with his forehand; he couldn’t seem to get it past the service line in the heavy, overcast conditions, and he couldn’t take advantage of the short balls that Dimitrov gave him. As for the Bulgarian, he showed the Monte Carlo crowd what he can do, and who they might be seeing a lot more of in the future. His backhand had more depth than normal; Nadal was unable to break it down. From the forehand side Dimitrov went from sliding defense to jumping offense in the same rally. He cracked two forehands over 100 M.P.H. and broke Nadal twice to win the second set 6-2.

For much of the third, it looked as if Dimitrov would hand Rafa his first loss on this court in 10 years—that would be 2003, when Grigor was 11 years old and Federer had yet to win a major title. Dimitrov was hitting with more pace and depth, while Nadal continued to have trouble doing any damage. After one backhand return that he plopped into the net for no apparent reason, Nadal put his hands up in frustration—“What is happening here?”

Yet he never looked panicked, even as Dimitrov stayed a game ahead on serve; eight straight titles in a place will do that for you. At 4-4, Nadal finally took his chance and stepped forward, and Dimitrov finally came undone. After one point, the Bulgarian cramped; on another, he broke a string. Nadal pummeled his backhand long enough to earn the break.

With Rafa serving at 5-4, it looked all but over, but Dimitrov wasn’t quite finished. He held off cramps to save one match point with a leaping, 105 M.P.H. forehand. On the next one, though, Nadal made sure he couldn’t do it again. He hit an ace for his 45th straight win in Monte Carlo, 6-2, 2-6, 6-4.

Nadal, despite 36 unforced errors against just 18 winners, and an eight for 20 ratio at the net—he also had his back taped—will move on to play Jo-Wilfried Tsonga. But this was a winning day for Grigor Dimitrov as well. He’s getting closer each month, it seems, to being all grown up.